In your hands the K-7 vs K10D

You will not be able to do that because of a couple of reasons.
1) it is a Li-ion battery so no NiMH
2) NiMH cells are 1,2V so you will never get to the 7,4V that the battery which goes into the K10D and K20D delivers with two AA batteries.

[edit]
7,4 volts is about 6,2 NiMH AA batteries so that is the reason why you can use 6 AA batteries in the K-7 battery grip.
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It's only your pinky that is more free but the rest of your fingers are still very good on the grip so if you buy a battery grip you wouldn't have that problem.

I don't believe the grip would be bigger then the bg-2 grip it's of course shorter so it might look more bulky.

I knew that was a concern for most so paid attention on that.
To be honest when you look at the camera it doesn't look a lot smaller and it doesn't feel small but if you set it beside the K20D you see the difference though. I didn't had it beside the K-M but it looked almost to be the same size.

So the K-M and then with the K20D grip, weight and quality that's how I would describe it.

Yes good one Remco didn't thought about the voltage

I'm surprised you could think that because the battery performs better than FOUR of the best NiMH AA cells, let alone two.

The K20D battery contains two Lithium ion cells. Li-Ion is better than NiMH in terms of power to weight ratio, power to size ratio and self discharge rate.

I know Pete, Remco told me all about it

1 AA Li-ion Cylindrical Rechargeable Cell: 3.7V 2600mAh link
$15.95

So two of those would mean 5200mAh, sound very interesting when comparing to 1620mAh battery pack from Pentax.

So do anyone have a dead battery for me?

two off those will give you 7,4 volts if you connect them in series. the capacity stays at 2600mAh.
You will only get to 5200mAh when you connect them parallel but that leaves the voltage at 3,7V.
Didn't pay attention at physics class Stefan?

[edit]
The battery you linked to is a 18650 which is quite a bit larger then an AA sized battery.
The 18650 is 18mm in diameter and 65mm in length (hence the name 18650).
I use these in my Ultrafire flashlight.
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it's already 6 years ago and electric wasn't my type of physics to begin with. It's indeed a big mistake that one
I failed the exam 2 times so that say enough I believe
The great thing is though that I've worked on some of the electrical systems of a couple Boeing 747 and one 777, happy flying

Edit:
so the question is if they will fit inside the K10D,
If they just deliver pwer to the contact and stay inplace I'm already happy. When you look what a battery pack cost it sin't really in comparison to be honest.

They also have batterypack of 7.4V 10000 mAH, might be interesting to see if they fit in a battery grip

The 18650's will not fit because the d-li50 is just over 50mm in height.
I have one original d-li50 and I have a np-400 replacement which surprisingly is the same size and voltage as the d-li50 and has the contacts at exactly the same position and those contacts have the exact same dimensions as the d-li50. (sorry John, I couldn't resist)
The np-400 replacement has a higher capacity as the d-li50 but not by a huge margin.
Personally I would only use batteries which have the correct dimensions instead of experimenting.

So you wouldn't use a Samsung SLB-1674 either? (that is the battery which came with the GX-10 and GX-20).

This reminds me of the program on the telly named Kassa, they talked about malls own brand products and those of AAA brand products and it apears that most of those products are made in the same factory and that only the package material is differend.

Here you go Stefan

There are only TWO battery manufacturers in the WORLD!!!
One makes all the GOOD Stuff and the other makes all the CRAP!!

shim

Great work Unlocker!
so that are 18500 batteries
Diameter 18.3 mm (Max 18.4), Height: 50.0 mm (Max 50.3) you see Remco I learn fast

You don't have such high capacity of those though
but still two new 1400mAh are $7.80, I don't know for how much new batteries go for the pentax.

But we know that this is the same battery, don't we? So this is a spurious point really.